The proliferation of sub-sea well drilling operations and the heavy cost incident thereto has created an urgent need for economy in many areas. For example, it has been customary to discard some costly equipment components after a single usage without any effort to salvage and reuse the same. Costly new components are sold to the customer for each new sub-sea drilling operation. Among the components which have been discarded after use are well head housings in which costly casing hangers and their seals are disposed. Each casing hanger seal when new costs as much as $3,000 and the new well head housing costs many thousands of dollars and when used only once represents an extreme economic burden on the customer.
This invention has been devised to deal with the above problem completely and economically so that the costly practice of discarding well head housings after only one usage can be eliminated. More particularly, the tool which embodies the present invention has the ability to efficiently test the internal sealing surfaces of well head housings to determine the integrity of such surfaces after usage in a sub-sea well, and in almost all cases, the testing indicates that the well head housing can be safely reused a number of additional times with a correspondingly great saving of money. Additionally, the tool according to the invention is used to test sub-sea casing hangers and their costly seals. By means of the identical tool, when run on a drill pipe string in a well and actuated with fluid pressure through the drill pipe, a given casing hanger seal can be isolated from blow-out preventer equipment to determine whether the seal is leaking, in which case the seal is replaced, or whether the source of the trouble is somewhere in the blow-out preventer.
Another very important aspect of the invention resides in the fact that the test and isolation tool itself is quite simple and comparatively economical in construction because of the fact that the tool employs discarded and slightly altered casing hangers and used casing hanger seals instead of new seals which cost up to $3,000, as stated. Each time a well is drilled at least one seal is used and usually two and these seals are discarded. The discarded casing hanger seals are the seals employed for the tool forming the subject matter of the invention. When the casing hangers are repaired, new seals are always used, and for the sealing surfaces of the hangers to have been tested with used seals and found to be satisfactory puts even a greater guarantee on the integrity of the surfaces, and this guarantee applies equally to the sealing surfaces of well head housings which are also tested by used seals on the test tool. The tool is also capable of testing casing hanger seals simultaneously with the testing of sealing surfaces on well head housings and casing hangers. Thus, the invention is very versatile resulting in a further savings of cost to the customer.
The prior art contains a variety of testing tools for well pipe and well head equipment and for well casing. The nature and construction of such tools varies widely depending upon the particular use or application of the test tool. Many prior art test tools are for the purpose of testing a full length of pipe or casing for leakage through pin holes, threads or couplings and not at specific local sealing surfaces, as is the case with the present invention. Suffice it to say, no known prior art device is constructed and arranged to satisfy the specific requirements which the present test and isolation tool meets, and to this extent the present invention is thought to satisfy a need of the art which heretofore has not been satisfied by anyone.
To comply with the duty to disclose known prior art under 37 C.F.R. 1.56, the following United States patents are made of record herein:
U.S. Pat. Nos. 2,951,363; 3,034,339; 3,048,998; 3,177,703; 3,199,598; 3,371,521; 3,478,577 and 3,712,115.
Other features and advantages of the invention will become apparent during the course of the following detailed description.